[Gradle, JS] Fix warning in case when js target declared twice

^KT-55099 fixed

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kotlin2JsGradlePluginIT.kt

@@ -1147,6 +1147,22 @@ abstract class AbstractKotlin2JsGradlePluginIT(protected val irBackend: Boolean)
         }
     }
 
+    @DisplayName("kotlin/js compiler warning")
+    @GradleTest
+    fun testKotlinJsCompilerWarn(gradleVersion: GradleVersion) {
+        project(
+            "kotlin-js-compiler-warn",
+            gradleVersion,
+            buildOptions = defaultBuildOptions.copy(jsOptions = defaultJsOptions.copy(compileNoWarn = false, jsCompilerType = null))
+        ) {
+            buildGradleKts.modify(::transformBuildScriptWithPluginsDsl)
+
+            build("assemble") {
+                assertOutputDoesNotContain("This project currently uses the Kotlin/JS Legacy")
+            }
+        }
+    }
+
     @DisplayName("dependencies are resolved to metadata")
     @GradleTest
     fun testResolveJsProjectDependencyToMetadata(gradleVersion: GradleVersion) {

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/testbase/BuildOptions.kt

@@ -50,6 +50,7 @@ data class BuildOptions(
         val jsCompilerType: KotlinJsCompilerType? = null,
         val incrementalJs: Boolean? = null,
         val incrementalJsKlib: Boolean? = null,
+        val compileNoWarn: Boolean = true
     )
 
     fun toArguments(
@@ -113,9 +114,13 @@ data class BuildOptions(
             jsOptions.incrementalJsKlib?.let { arguments.add("-Pkotlin.incremental.js.klib=$it") }
             jsOptions.useIrBackend?.let { arguments.add("-Pkotlin.js.useIrBackend=$it") }
             jsOptions.jsCompilerType?.let { arguments.add("-Pkotlin.js.compiler=$it") }
+            // because we have legacy compiler tests, we need nowarn for compiler testing
+            if (jsOptions.compileNoWarn) {
+                arguments.add("-Pkotlin.js.compiler.nowarn=true")
+            }
+        } else {
+            arguments.add("-Pkotlin.js.compiler.nowarn=true")
         }
-        // because we have legacy compiler tests, we need nowarn for compiler testing
-        arguments.add("-Pkotlin.js.compiler.nowarn=true")
 
         if (androidVersion != null) {
             arguments.add("-Pandroid_tools_version=${androidVersion}")

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin-js-compiler-warn/build.gradle.kts

@@ -0,0 +1,22 @@
+import org.jetbrains.kotlin.gradle.plugin.KotlinJsCompilerType.BOTH as BOTH_TYPE
+
+plugins {
+    kotlin("multiplatform")
+}
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
+
+kotlin {
+    js(BOTH)
+    js(BOTH_TYPE) {
+        useCommonJs()
+        browser {
+        }
+    }
+    js {
+
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kotlin-js-compiler-warn/settings.gradle

@@ -0,0 +1,5 @@
+rootProject.name = "kotlin-js-browser"
+
+include("base")
+include("lib")
+include("app")

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/dsl/KotlinTargetContainerWithJsPresetFunctions.kt

@@ -85,8 +85,10 @@ private fun KotlinTargetContainerWithJsPresetFunctions.jsInternal(
 ): KotlinJsTargetDsl {
     val existingTarget = getExistingTarget(name, compiler)
 
-    val compilerOrDefault = compiler
-        ?: existingTarget?.calculateJsCompilerType()
+    val kotlinJsCompilerType = (compiler
+        ?: existingTarget?.calculateJsCompilerType())
+
+    val compilerOrDefault = kotlinJsCompilerType
         ?: defaultJsCompilerType
 
     val targetName = getTargetName(name, compilerOrDefault)
@@ -111,7 +113,7 @@ private fun KotlinTargetContainerWithJsPresetFunctions.jsInternal(
         ) as KotlinTargetPreset<KotlinJsTargetDsl>,
         configure
     ).also { target ->
-        warnAboutDeprecatedCompiler(target.project, compiler ?: compilerTypeFromProperties)
+        warnAboutDeprecatedCompiler(target.project, kotlinJsCompilerType ?: compilerTypeFromProperties)
     }
 }